I've noticed the spacing between my periods have become quite irregular, I used to get my period every 28 days, in the past few months its been 24, 29, 19, 25. Before my last two periods I've begun to experience mild period-like cramping 4 days before I get my period. This is unusual for me as I have only ever gotten cramps during my period. My periods have remained to be normal in length (5 days) and flow (very heavy and painful first 2 days and light afterwards). I'm a little concerned and unsure as to what could be causing these irregularities, Im not on BC and am only 20yrs old.